1. Field of the Invention
The present invention concerns systems, denoted in the following with the acronym SAV, for supporting and actuating, in particular, surgical and diagnostic instruments, limb prostheses, toys, diagnostic instruments for the industrial field, etc. The systems include mechanical elements, i.e., links, generally equally arranged in vertebrae fashion, and a group of cables.
In a preferred general embodiment of the invention, the vertebrae links are arranged serially so as to form a three-dimensional open kinematic chain, wherein every vertebra (1b) forms, along with the preceding vertebra (1a), a rotational kinematic pair with an excursion, generally symmetric, having an angle in the range of .+-..alpha. and constituting an elementary module in which the following (SUCC) vertebra (1b) has two directions of rotation with respect to two mutually orthogonal axes, both orthogonal to the axis of the preceding (prec) vertebra (1a), named P and Y (Pitch and Yaw). The actuation of these two movements is performed by means of cables (7) associated with the kinematic chain of vertebrae.
2. Description of the Related Art:
The need for systems for support and actuation with a high level of articulation becomes more and more intense as technology evolves along with the related increase in sophisticated user demands. To cite some examples, in many surgical interventions it is necessary to introduce instruments inside the human body with the aim of observing the operating scene by means of suitable optics and/or of intervening with tools. The instruments devoted to this goal are formed by a distal end, a medial shaft and a proximal end. The instruments are grasped by an operator in the neighborhood of the proximal end whereas the optics and the tool are in the distal end. Although in some procedures it is sufficient to use instruments having a rigid medial shaft, in most cases it is necessary that the instruments possess a certain amount of dexterity in the distal end, which typically results in an increase in the invasivity of the procedure or, even worse, the impossibility to execute it. In flexible steerable endoscopes, (colonoscopes and gastroscopes) it is possible to steer the tip of the distal end of the instrument.
A flexible steerable endoscopic instrument has a circular section and includes a proximal end, a distal end and a flexible shaft connecting the proximal end and the distal end. The curvature of the distal end can be modified by means of a suitable actuation system, normally including a set of sheathed wires, controlled by the operators by means of wheels located in the handle. The proximal end of the instrument is attached to the handle. In this way it is possible to steer the tip of the distal end in a desired arbitrary direction. The flexible shaft, in addition to housing the sheathed actuation wires, possesses some channels located close to the longitudinal average curve of the instrument. Such channels can be used for passing-through fiber optic and/or mechanical transmission means devoted to the actuation of an instrument attached to the distal end.
Flexible steerable endoscopes are used for diagnostic purposes and for this reason an optical channel (usually an optic fiber) allows both the illumination of the body part to be explored and the transmission of images thereof. They can also be used as surgical instruments in the case where they have an operating channel which allows the introduction of a suitable tool (gripper, scissors, electro-scalpel, electro-coagulator, etc.).
In European Patent No. 0 427 949, the Applicant has already described a circular stapler featuring a suturing head located in a suitable location, for example, mounted at the end of a flexible shaft consisting of at least a traction wire and spherical joints, preferably made of polymeric material.
An example of an endoluminal steerable circular stapler is shown in European patent application EP 0 540 020 A2 (FIGS. 1 and 1A). The inventors, however, do not specify either the kinematic configuration or the constructive solution used to implement the distal steerable end.
In U.S. Pat. No. 5,383,880 a linear staple with a flexible shaft actuated by means of an electric motor placed in the handle is described. Sensors are present to allow control through a dedicated unit. The system, however, lacks the possibility to purposely steer the end tool placed in the distal end of the instruments. Furthermore, it is not possible to change the end tool easily, during an intervention, in order to execute several sutures. The description of the sensory given in the "Detailed Description of the Invention", is generic and does not clearly explain which parameters are used and how to measure them.
An example of actuation with vertebrae is shown in International Patent Application No. WO 92/01414 (FIG. 2A) where the vertebrae forming the structure of the distal end are articulated by means of spherical joints allowing also a rotation of a vertebra with respect to the axis of the preceding vertebra. Such rotation cannot be controlled by the actuation wires of the device and, as a consequence, it is impossible to obtain a suitable torsional stiffness. In the present invention, the kinematics of the articulations and the shape of each vertebra allows for obtaining suitable increased torsional stiffness.
Another example of a mechanism providing a solution to the problem of torsional compliance of the shaft of a steerable instrument is described in International Patent Application No. WO 94/17965 (FIG. 1): the mechanism is planar and consists in a chain of articulated, crossed four bar linkages with rigid links allowing to change the curvature of the linkage in its plane under the power of a suitable actuator. This solution ensures adequate stiffness in any direction, but it is planar, so it allows only steering of the instrument tip in a plane.
The system described in International Application No. WO 90/05491 (FIG. 1) includes a steerable distal end made with vertebrae that allows for placement of a tool for the application of a staple for aneurysm. The vertebrae configuration does not allow correct kinematic operation of the mechanism because the average curve changes its length during operation. As a consequence of the change in the length of the average curve of the instrument, the instrument itself is not suitable for guiding fiber optics. In addition, another consequence of the change in the length of the average curve is that the actuation cable passing through the vertebrae is deformed as a consequence of bending of the instrument, and this may cause improper and/or undesired operation of the actuated tool.